I simply don't trust any Windows utility to correctly deal with OS X when adjusting disk drive parameters.
Any time I have found the need to adjust the Windows partition, I have used WinClone to save my installation (I use it anyway as a periodic backup utility), then use OS X BootCamp Assistant to totally remove the Windows partition back to full disk OS X. I then start over again with Bootcamp Assistant and create new partition of the desired size ... and then use WinClone to restore my Windows installation and expand it to utilize the full partition size. All operations are performed in OS X! 🙂
It sounds tedious ... but it has always worked for me without fail ...
Others may have a more straight forward method which they have proven to work.